| 摘要 |
<p>Provided is a toning circuit (5) for a liquid crystal back light. This toning circuit (5) comprises a photo diode (9) for outputting a monitor current according to the intensity of a light emission from a back light (3), a light emission intensity monitor unit (13) fed with the monitor current for generating a light emission intensity signal corresponding to the storage quantity of electric charges due to the monitor current for a measuring time period from the reset signal generation to the hold signal generation, and a controller (7) for generating a control pulse signal to control the light emission of the back light (3) by a PWM control, in accordance with the light emission intensity signal, and for generating the reset signal and the hold signal such that the repetition period of the measurement period may be N (N: an integer of 1 or more) times as large as that of the control pulse signal, thereby to output the control pulse signal and the hold signal to a light emission intensity monitor unit (13).</p> |
